During travel and in other situations, it is common practice to convert the prices of goods and services expressed in a foreign currency into one's own home (or other) currency. To obtain the equivalent value in one's own currency, the foreign price is multiplied by the home currency/foreign currency exchange rate either mentally, manually with pencil and paper, or with the aid of a portable electronic calculator
While currency conversion is simple in principle, complications all too frequently have arisen in practice. The mental calculation technique is subject to computational error, particularly where the price is large and/or the exchange rate is an unruly decimal or ratio. In addition, the mental calculation technique always calls for a modicum of concentration, and mental stress may be introduced, particularly where the situation is "busy" or otherwise does not readily allow the mental calm necessary to perform the calculation.
The manual calculation technique is also subject to human calculation error, and suffers the further disadvantages that even when pencil and paper are readily available, the time and effort involved in performing the calculations may be experienced as disruptive, and may heighten the sometimes uncomfortable feeling of being in a foreign land far from home.
While free from computation error, the use of a calculator is encumbered by the need to remember, and to enter, the exchange rate separately for each price conversion. In addition, the situations where each conversion is to be calculated are often such as to disturb mental calm, and anxieties may arise either from worry that the correct form of the exchange ratio has been entered or that the calculation has been accurately performed.
Calculators pre-programmed to do currency conversion have been devised in the effort to help alleviate these difficulties. The single-foreign/single-home currency exchanger commercially available from Magellens.TM. is representative of this class of devices. In use, the exchange rate to be employed is first manually entered and stored in the currency exchanger, and thereafter, each foreign price is entered and the currency exchanger automatically converts it to the home currency.
The heretofore known single-foreign/single-home currency converters have been disadvantageous in multi-country travel and other situations. Not only has the old exchange rate had to be cleared and the new country's exchange rate manually entered with entry into each new country, but also it has not been practicable to perform multiple, cross-country currency conversion. Moreover, the user interfaces of the heretofore known single-foreign/single-home currency converters have generally been less than intuitive. Displaying only a numeric field, the heretofore known devices were subject to uncertain data entry, and to a lingering suspicion that somehow the conversion may have been unreliable.